Our laboratory is engaged in the following studies: 1) Elucidation of the structural and quantitative differences between rapid and slow N-acetyltransferases from humans and mice, the acetylator phenotype of which is determined both in vivo and in vitro, by: (a) assessment of the complete N-acetyltransferase (NAT) gene sequences; (b) comparison of the size, relative abundance, and stability of the corresponding NAT mRNAs, and (c) expression in heterologous systems, encompassing experiments on the kinetic and physicochemical properties of expressed variant NATs with those of the wild type, 2) Development of assays using biotinylated, allele-specific oligonucleotide probes for distinguishing rapid and slow human NAT genes.